I'm bearish on a hydrogen economy based on the gasoline-refueling model because H2 just hates being cooped up in tanks and pipelines. So my ears perk up when they hear about schemes for generating hydrogen on board and on demand. The latest one hails from Purdue University and involves separating hydrogen from water on board using elemental aluminum.You've probably never seen elemental aluminum. Because of its affinity for oxygen, your Diet Coke cans and Z06 chassis are all coated with a thin layer of aluminum oxide. But when raw aluminum touches water it hijacks the oxygen molecules simultaneously forming alumina (Al2O3) and releasing heat and hydrogen gas, as Jerry Woodall was startled to discover while working as a young IBM semiconductor engineer in the 1960s. He was rinsing out a crucible containing a liquid gallium-aluminum alloy when, poof! hot hydrogen appeared. He deduced that in this liquid alloy, the aluminum molecules were able to migrate to the surface where the water was, bond with oxygen, and float away as alumina, while more molecules churned to the surface to keep the reaction going, eventually leaving pure gallium liquid, alumina powder, and water when the pure aluminum was depleted.

The initial alloy was mostly gallium, which is so expensive that even though it doesn't get consumed, the process didn't look promising for economical hydrogen production. But more recent research has shown that alloys of 95-percent aluminum with three-percent gallium and some cheaper indium and tin can still split water, producing 14 BTU/lb of energy-half as pure hydrogen gas, half as heat. Now the system begins to look more viable, especially considering the leftover alumina powder can be electrically recycled back into aluminum alloy.Woodall reckons a typical midsize fuel-cell-powered car would need to carry 115 pounds of alloy pellets and 50 pounds of water to go 350 miles. At today's economics, the alloy would cost $0.70/pound, or $80.50. (By recovering half the water coming out of the fuel cell, this system reportedly meets the Department of Energy's 6.0-percent hydrogen storage density target.) A midsize gasoline-powered car averaging 27 mpg needs 13 gallons (84.5 pounds, $39 at $3/gallon). These costs assume recycling the material 19 times by a process that's 50 percent efficient using nuclear energy produced on site. Such a car would likely be refueled by swapping the spent tank for a fresh one, after which the alumina slurry could be pumped out and piped, trucked, or shipped to a regional recycler.Woodall cites U.S. Geological Survey studies suggesting there's plenty of economically recoverable aluminum and gallium to fuel the fleet. Argonne National Labs will soon conduct a thorough well-to-wheels energy-efficiency and CO2 analysis. The two-way transportation of the aluminum will certainly deflate those numbers, but harnessing the heat released on board to run a steam turbine or Sterling engine could improve them. It's difficult to envision an aluminum-alloy pellet distribution network springing up any quicker than a hydrogen one, but as a non-volatile, non-flammable, non-toxic material it has some serious upside potential-particularly in terms of customer acceptance. Aluminum-alloy pellets conjure no Hindenburg imagery.In 2006, Purdue licensed the technology to the startup AlGalCo for commercialization, and its first products will likely include fuel-cell emergency auxiliary power units (the alloy remains stable indefinitely until water hits it). As for automotive applications, Woodall envisions starting out with a small 10-kW-hr AlGalCo-fed fuel-cell serving as an emergency range-extender carried aboard plug-in electric vehicles, providing enough oomph to drive 20 miles home to a plug. Imagine, hydrogen serving as a safety net.